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Gravitational Potential Energy & Black Holes:

What To Do for Conservation of Energy Labs?

The answer depends heavily on what the students have already had in a previous physics course (if any).
If your students have had a strong first course that included a good C of E lab then you probably need to nothing for a base C. of E. lab and wait until you cover rotating objects. When I do a lab to “Verify” – here come the modelers after me – that Torque = I alpha by dropping a hanging mass attached to a rotating wheel, I also have them compute all the energies in the system (usually three – PEg of dropping mass, KE of dropping mass and rotational KE of spinning wheel – and the sum) and plot the four energies as a function of time. The Peg drops as the two KE’s rise and the sum remains constant.
If you are a Physics C first, you can do what we do in our honors course (and in fact are doing right now at our school in our 4x4 sections, but not our 4x4 A/B sections) which is to think of any moving system that can have the motions measured. If you can measure the motions (position and time) you have a C. of E. lab. We usually let the kids pick from a class generated set of possibilities including using data from prior labs in some cases. The following are nice candidates for C. of E. labs.
  1. Simple pendulum. Set of a video camera and tape ONE swing. Measure heights at each frame and average velocity between frames. Voila, you have PE and KE. Add them up at each time and you will get a pretty straight and horizontal line. This is the lab that PSSC physics from the 60’s attacked C. of E.
  2. Pendulum with a stop along the rope that forces the radius arm to shorten. Still works fine as #1.
  3. Put a block on a hill and let it slide. Measure position and time with a sonic ranger, or a spark timer or a TV camera. If the kids measure the coefficient of kinetic friction well, they can compute change in PE, KE and FE (frictional work). The sum will again be constant.
  4. Pull the block up a hill by a falling mass (use a good and light pulley). Now you have 2 KE’s 2 PE’s and Frictional energy. Measure the motion of eith mass and you KNOW everything.
  5. Hang a mass on a spring. Using a sonic ranger or sparktimer measure ONE (half cycle). PE, KE and SE (spring energy). Warning, this experiment is sometimes sensitive enough to show some strange error because one really must account for the change in PE of spring and its KE. We solve this by making the hanging mass MUCH LARGER than spring mass.
  6. Use a spring to pull a block up a table.
  7. Earlier in the year we tossed a basketball across the room in front of a video camera to compute projectile data. This data is also a C. of E. lab. With KE and PE staring at you in the table, though the kids did not compute it at that time.
  8. When measuring ‘g’ earlier, one of the labs we do is toss a basketball straight up in the air over a sonic ranger. Voila you have another simple KE and PE C. of E. lab.
  9. Build an Atwoods machine. One mass falling, one mass rising. Time one of the masses. (We usually use one of the cheap tiny spark timers in a box devices and let the rising mass pull the tape behind it. 2 KE’s, 2 PE’s. Works nicely.

Basically, if you can measure coefficient of sliding or rolling friction, or measure the spring constant AND measure the motion of the object, you can always do a C. of E. experiment.
David Green
Posted by Bill Taylor

Spring Toy Lab.

Students must design 2 independent experiments to determine both the launch velocity and spring constant of a toy. Lots of different toys can be used: Hot Wheels launchers, ice cream cone shooters, spring jumpers, nerf ball/dart shooters, etc. I find it useful to have each group map out an experimental design on a whiteboard before allowing the group to take data. The grading rubric is modeled after Eugenia Etkina's scientific abilities rubrics. Frank Noschese

Web Resources in Forces, equilibrium and more (by the College Board).

Conservation of Energy open-ended lab:

Energy & Work Notes:

Here are my notes from the chapter on Energy and Work. It's basic, but I feel sums up the important definitions in a small package. I always have my students read these notes before we begin the chapter. Contributed: Mark W. Hossler

Work & Energy Notes: Notes from Wayne Mullins.
Wayne's (now somewhat old) notes can be accessed at

Human Power Lab.

Lab 1: Using various muscle groups of the human body, have students calculate the power output they can generate. Written by Mike Maloney, posted by Bill Taylor

Human Power Lab 2. Stair climbing and pushups, using the Vernier force plate and motion detector for pushups. Written by Doug Hutton

Bungee Jumping GI Joe Design Contest.

A competition where kids use conservation of energy analysis along with engineering iteration programing in EXCEL to design a bungee cord made of rubber bands in series that will stretch a certain distance when dropped.

  • The students receive the first page and do the energy analysis themselves to get the complicated equation seen on the second page, usually for homework after we have done conservation of energy..
  • I would have a conservation with them about their results, and give them the second page telling them how something like that could be solved via iteration. Depending on the computer literacy of the class, this might also include a tutorial in EXCEL, but by this point in my class they have used it enough on other labs to be proficient in it.
  • They next create an EXCEL sheet (like the included example) to do the iteration and get a theoretical rubber band number for their bungee.
  • Next they create their bungee by tying together rubber bands, test it, and then compete.

I use this as a overall theme for my unit on energy, telling them about it as their goal for the chapter, and as we go through they learn about PEgrav, KE, PEspring, and conservation of energy... and then put it together in this project at the end, usually with the competition the class after a test. It is a nice way to give a practical example of the conservation of energy, and also to show them some simple engineering, where they theoretically create a design, make a prototype, test it and modify it to match real life, then compete with it. You can also bring up how in real bungee jumping different bungees are used depending on the height and the mass of the jumper.

We drop from over 50 ft in a stairwell of my school, and usually I get a few groups that get around 10 cm from the ground. You can check out a video here that shows my winning students one year whose egg (I used to use eggs) actually dropped pass my camera lens (laying on its back) but never touched the ground, it was about 2 cm from the ground.

Written by Mike Maloney
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Bungee Jumping Lab:

  • from plulai
  • Here is an Excel file I use. The kids calc x, l, h for their first run through, then plug into excel to get these values from multiple iterations.
  • Use sheet 2 of the excel file. I have the kids plug in the values for the yellow fields. It isn't pretty, but it works great. I use lengths of rubber tubing I bought at a local hardware store.

Adjustable Roller coaster Energy Problems

~ Dan Hosey

Bungee Jump Lab with Hooke's Law Springs

Dan Burns

Hopping Toy Lab based on the 2009 AP B Free Response #1 -

Dan Burns

Goldeneye Bungee Jump Analysis PowerPoint and movie clip

- Dan Burns

Resurrecting Feynman -

How to use an audio recording of Feynman lecturing Cal Tech students about conservation of energy to introduce this subject to your students. Below is a teacher's guide, the edited audio file, a companion slideshow, and a slo-mo movie that goes with the slides. Have fun resurrecting Feynman in your class. - Dan Burns

Spring Lab

- A basic conservation of energy lab using an extension spring and cart/track. - Dan Burns

Work-Energy Theorem Guided Inquiry Investigation

Uses Dynamics carts, force sensors, and photogates to lead students to derive the work-energy theorem. Also has them investigate basic conservation of energy. It's a very long lab so you may want to only use parts.
Email me with any questions - Tom O'Dell,

AP Physics 1 Work energy Power Problem Set

AP Physics 1 Work Energy Power Problem Set - Problem set built by Bob Enck, Dan Fullerton and Paul Sedita in an effort to start an AP-1 style problem bank. Feel free to print/use in your classrooms. Please don't re-post the files themselves, but rather only the links to the files, to allow us to quickly and easy update and continue to build upon these problems. Thank you! -- Dan Fullerton ( PS - anyone interested in adding on to these problems, we'd love the help!

PhET Masses and Springs Hooke's Law Activity
Students use F=kx to find spring constant without knowing actual x, find length of spring, find unknown mass, then g on Planet X. Good practice for Hooke's Law. - Dan Burns